Laser-induced fluorescence of NaK: the b(1)3Π state

Laser-induced fluorescence of the NaK molecule has been recorded at high resolution by Fourier-transform spectrometry in the region 4000-9500 cm -1 . Fourteen series excited by the Ar + 4765, 4880 and 5287 AA lines have been assigned to the system D 1 Pi , d 3 Pi to b 3 Pi . The strongest transitions, at low values of J, are Omega =1 to Omega =1, but there are also series that arise from Omega =2 to Omega =2 and from Omega =0 to Omega =0. The lower state, the second excited triplet state of NaK, has not been observed before. Constants (in cm -1 ) for b 3 Pi 1 are as follows: T e =11562.18, omega e =120.41, omega e x e =0.3425, B e =0.095066 and alpha e =3.28*10 -4 . The spin-orbit coupling constant A is estimated to be 15.577 cm -1 and the internuclear distance r e is 3.502 AA. The results are in good agreement with pseudopotential and ab initio calculations.